The effectiveness of advanced (300 hours plus basic 81 hours) versus basic (81 hours) emergency medical technicians (EMTs) in providing prehospital care for suspected cardiac patients will be examined in a comparative, community-based study. Over a three and a half year period, approximately one-half of the residents of Cape Cod utilizing ambulance services will be cared for by advanced EMTs; one-half will be cared for by basic EMTs. Operational constraints suggest that assignment of patients will be non-systematic though non-random. Patients in the two groups will be retrospectively matched by severity of condition, and all relevant socio-demographic variables. Two process variables will be assessed: the EMTs' recognition of patient symptoms and EMTs' treatment of patients. The outcome variable of proximal mortality in the Emergency Room and the hospital will be assessed.